1. Field of the Invention
High-orientation graphite has an outstandingly high ability of reflecting radiation, and such graphite is used in medical low-energy neutron reflectors, neutron-ray monochromators, x-ray monochromators, and reflectors of nuclear fusion reactors.
This invention generally relates to a method of carbonizing high molecular compound, and more particularly the method of the invention is characterized in that high-orientation sheet-like graphite is made by preliminarily carbonizing a high molecular compound in a space between layers of laminar compound, the high molecular compound being one of various types, removing the carbonized compound from the space between the layers of laminar compound, and graphitizing the carbonized compound.
An object of the invention is to facilitate production of high-orientation sheet-like graphite by using a two-dimensional field for carbonization of high molecular compound, which compound can be one of various types.
2. Description of the Prior Art
High-orientation graphite has been produced in the form of Kish graphite, high-orientation pyrolytic graphite (HOPG), and the like. Kish graphite is produced by carbon precipitation from molten iron, and it provides graphite crystals of high quality. However, Kish graphite has a shortcoming in that its crystal is very small, and it is hard to apply to practical use. On the other hand, HOPG is produced by either compression of pyrolytic carbon or heating of pyrolytic carbon under stress at a high temperature above 3,200.degree. C. Pyrolytic carbon can be obtained by gas-phase heat decomposition of hydrocarbon gas. However, HOPG has a shortcoming in that the amount of its production is limited and it is costly, because the assembling speed of pyrolytic carbon is very slow and heat treatment under stress at a very high temperature is required.
Since graphite is neither soluble nor fusible due to its extremely sturdy molecular structure, in order to obtain high-orientation graphite, a special synthesizing process is necessary for preparing graphite in the form of membranes or fibers with a highly orientated structure. It is noted, however, that those macromolecules, which can be carbonized without being melted or softened for maintaining its structure intact after the carbonization, have three-dimensional crosslinking of molecular chains developed therein during synthesis thereof, or that the three-dimensional crosslinking tends to be developed in such macromolecules during the heat treatment for graphitization. Thus, in order to produce high-orientation graphite from such macromolecules, there is a pressing need for research and development on a method of preparing macromolecules having such a high-orientation that can be kept intact during the ensuing graphitizing treatment.